Relatively thin rods of a ceramic material loaded with a strong abrasive have been used successfully to sharpen knives and other blades. See U.S. Pat. No. 3,894,362 to Louis N. Graves, granted in July of 1975, Class 51/211 R. In this sharpener, the cylindrical ceramic rods are supported in a horizontal base so that the angular relationship of the longitudinal axis of each rod to horizontal will be such that the desired angle of contact of the blade being sharpened with respect to each rod will be achieved when the vertical blade is held in a vertical plane at right angles to a vertical plane including the rods. This makes it imperative or at least very important that the operator sharpening a blade hold the blade in an exactly vertical plane at right angles to the plane of the rods on each sharpening stroke down the rods. This angular relationship is not always easy to maintain consistently throughout the sharpening process.
Furthermore, the direction of motion during sharpening of the blade is downwardly toward the base which supports the rods, and this can result in a scarring of the base and/or a dulling of the blade being sharpened whenever, as sometimes happens, there is an inadvertent overrun of the blade with respect to the base.
The use for sharpening of the thin cylindrical ceramic rods, loaded with an abrasive substance such as aluminum oxide, has been well accepted. However, some means of immediately and consistently setting the angle of the blade with respect to the rod prior to each sharpening stroke was needed; and some means of supporting the sharpening rod in a horizontal position so that more weight could be brought to bear on the blade as it moves along the length of the cylindrical sharpening rod was desired.
It has been well known for many years to sharpen "butcher's knives" using a "butcher's steel sharpener". These sharpeners include an elongated narrow cylindroid rod of steel sharpening material and a concentric handle at one end of the rod, with a guard between the handle and the sharpening rod to insure that the user not accidentally slice himself with the knife in the process of sharpening it.
To sharpen high carbon steel knives with this "butcher steel sharpener", the knife is to be drawn over one edge of the sharpener at a 15.degree. to 20.degree. angle on one side and then on the other. No means other than what the operator conceived to be a "15.degree. to 20.degree. angle" was provided. Therefore, the effectiveness of the sharpening varied from operator to operator, and customarily an experienced butcher would not allow an apprentice to sharpen his knives because the apprentice would inevitably affect the efficiency of the knives by sharpening them at something other than the accustomed angle.
To overcome these deficiencies in the prior art, the blade sharpeners of the present invention were developed.
The applicant has made no preliminary search of this invention, and neither the applicant nor his agents is aware of any prior art which anticipates the claims herein. Applicant and his agents know of no prior art closer than that discussed herein and cited in the aforementioned U.S. patent, namely U.S. Pat. No. 1,223,127 to Walker, granted in April of 1917, Class 51/211 R; and U.S. Pat. No. 2,674,072 to Lohmann, granted in April of 1954, Class 51/211 R.